POS0740 VALIDATION OF THE PEDIATRIC BEHÇET DISEASE CRITERIA (PEDBD): A REAL LIFE CONSENSUS-BASED APPROACH
Authors: C. Matucci-Cerinic, H. Palluy, S. Al-Mayouf, P. Brogan, L. Cantarini, A. Gül, O. Kasapcopur, J. B. Kuemmerle-Deschner, S. Özen, D. Saadoun, F. Shahram, E. Mosci, N. Ruperto, M. Gattorno, I. Koné-Paut
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Behçet's syndrome (BS) is an autoinflammatory disease characterized by a variable vessel vasculitis. In children, BS may start early in life, mimicking other autoinflammatory diseases and making the diagnosis challenging. In the past, several criteria have been created for adult BS classification. In 2015, the first set of BS paediatric classification criteria, the PEDBD, was proposed by an international Expert consensus [1]. <h3>Objectives</h3> to perform an external validation of the PEDBD criteria in a cohort of internationally validated paediatric BS patients. <h3>Methods</h3> 210 patients (70BS, 40 PFAPA, 35 FMF, 26 MKD, 22 TRAPS, 17 UND/ SURF) were randomly selected from the Eurofever Registry (patients excluded if &gt; 16 years and if included in first PEDBD study). A set of 11 Experts blinded to original diagnosis, were chosen to evaluate the patients: in the 1<sup>st</sup> round, clinical and serological data were evaluated; in the 2<sup>nd</sup> round genetic data were added; in the 3<sup>rd</sup> round the other Experts' votes and comments were shown. Using the expert consensus as gold standard (agreement&gt;80%), the PEDBD, the ISG and the ICBD criteria were applied to BS patients and to the confounding diseases in order to define the sensitivity, specificity and accuracy. <h3>Results</h3> At the end of the 3<sup>rd</sup> round, a consensus on the initial diagnosis was reached in 112/210 patients (53.3%), with an additional consensus on a different final diagnosis in 27 patients. The BS patients with an agreement (24) were classified as confirmed-BS, and those with an agreement of 60-70% (10) as probable-BS. In confirmed-BS patients, oral ulcers were present in all the patients, genital ulcers in 77%, skin manifestations in 50%, a positive pathergy reaction in 39%, anterior and posterior uveitis in 29 and 27%, retinal vasculitis and papillary oedema in 8% of patients, with a resulting impaired vision in 17%. Venous thrombosis was present in 2 patients (8%). The patients with ocular and vascular involvement were all males. Cranic nerve palsy (17%) was the most frequent neurologic symptom. Abdominal pain was present in 33%, diarrhoea and gastrointestinal bleeding in 13% and anal/perianal ulcers in 8%. 29% presented arthralgia, and 13% arthritis. Fever was present in 50% of patients. HLA-B51 was positive in 69% of patients. When comparing these patients with the confounding diseases, an older age at disease onset, the presence of oral and genital ulcers, skin papulo-pustular lesions, a positive pathergy test and posterior uveitis were BS distinctive elements. The ISG, ICBD and PEDBD criteria were applied to confirmed and probable-BS and to the confounding disease controls, resulting in the following test characteristics (Table 1). <h3>Conclusion</h3> the PEDBD criteria were extremely specific but had a lesser sensitivity than ICBD which had a better accuracy. One limitation is that specific monogenetic BS mimics were not included as disease controls, thus the true accuracy of all these criteria may be lower in practice. The complexity of childhood BS suggests that genotyping (incorporating autoinflammatory diseases, BS mimics, and HLA-type) combined with clinical features are likely to yield the most accurate classification criteria, which would require further validation in a larger cohort. <h3>Reference</h3> [1]Koné-Paut I et al. Consensus classification criteria for paediatric Behçet's disease from a prospective observational cohort: PEDBD. <i>Ann Rheum Dis.</i> (2016) 75:958–64. doi: 10.1136/annrheumdis-2015-208491 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.